When implanting a knee prosthesis, it is necessary to incise the anterior face of the knee and to recline the corresponding soft parts, i.e. disengage these soft parts rearwardly so as to render the operative field more visible and thus allow the surgeon to access the femoral and tibial epiphyses articulated on each other, particularly the femoral condyles and corresponding tibial articular cavities.
U.S. Pat. No. 5,380,331 discloses using various retractors intended to facilitate access and treatment of osseous or ligamentary zones of the knee operated on, depending on the stage of operation underway. This type of retractor is in the form of an elongated rigid body of which the distal end is introduced at the level of precise interstitial zones of the knee in order to raise, hold back and/or disengage muscular, osseous or ligamentary parts of the knee. U.S. Pat. No. 5,380,331 thus envisages retractors of the tibia, the posterior ligament, the collateral ligament, etc. as well as patellar retractors of which the distal end, inclined with respect to the rest of the rectilinear body of the retractor, is applied against the outer lateral face of the tibial epiphysis in order to hook on the lower part of the quadriceps muscle tendon and dislocate the patella contained in the upper part of this tendon. Such patellar retractors prove in practice to be inefficient insofar as, by elasticity of the quadriceps muscle tendon, the patella tends to resume its initial place such that only a small extent of the lower zone of the tendon is efficiently disengaged towards one of the lateral sides of the knee. The surgeon is in that case often obliged to use these patellar retractors to force on the quadriceps muscle tendon and completely turn the patella round, risking damage to the tendon and/or the patella. In addition, as these patellar retractors abut against the outer lateral face of the tibia, their use requires a long and deep incision of the soft parts of the knee, even if the purpose of the operation is to implant a unicompartmental prosthesis, i.e. a prosthesis to be implanted only on one of the external or internal sides of the knee.
In the domain of implanting unicompartmental knee prostheses, intramedullary patellar retractors are known whose distal end is in the form of a rod and is to be introduced in the medullary cavity of the femur, after having previously bored an access to the cavity through the femoral epiphysis. Although, in practice this type of retractor limits the stress of the quadriceps muscle tendon and of the patella during reclination of the patella, the necessity of accessing the femoral medullar cavity leads to a long operation, which destroys the patient's osseous matter and is particularly invasive.
It is an object of the present invention to propose a patellar retractor which makes it possible to recline the patella efficiently without everting it, i.e. without turning it completely on itself, in order to offer the surgeon a good field of vision for the operation, while limiting the extent and depth of the incision necessary for use thereof, in particular which does not necessitate accessing the medullary cavity of the femur or of the tibia, and which is thus more particularly adapted to the implantation of a unicompartmental prosthesis.